Signal transmitting and receiving system



Feb. 6, w K SIGNAL TRANSMITTING AND RECEIVING SYSTEM Filed June 22, 1957 &mentor I attomei sGNAL TRANsNnm-rmGANnnEcEIVmG i I msizs'rEM w I P nted Felrplmo Radio Corporation of America., a corporatio o! Delaware Application June 22,

937, s ria No. 149521 This invention relates to` signal transmitting and receiving systems such as are useful in hear-` ing aids for the deaf or' in cases where a listener frequently moves from one location to another,

and has for its principal object the provision of an improved ap-paratus i and method of operation whereby the weight and Complexity of the equipment required to be carried by a moving listener is greatly reduced. v i

Further objects of the invention are the provision of (1) an improved apparatus for making radio programs readily heard bythe deaf, (2) an improved short wave receiver including means for automatically maintaining its Volume at a predeterminecl level irrespective of movement of the listener or others in his vicinity and (3) a simple` and compact transmitting and receiving system which may be readily utilized either as an adjunct to the ordinary radio receiver or as a desk unit for the transmission of intelligence to the deaf. r

More particularly, the invention contemplates the provision of 'micro-wave transmitter connected to the output of an ordinary radio receiver 25 and a micro-wave'receiver adapted to be carried by the listener. In the operation of a system of this character, it isfound that movement of the listener or` movement of others in the vicinity of the listener producesin the field pattern at the receiver` variations which adversely affect the received sound. This difficulty is avoidedin accordance with the present invention by the provision of improved means for automatically suppressing such variation. As will hereinafter more fully appear, the Volume variation suppres- 'sion means may assume the form of (1) a Volume leveling device such' as a biased crystal detector or, (2) a micro-ammeter controlled variometer i -shunted across the telephone receiver.` i 6 The invention will be better understood fro i the following description when considered in connection With the accompanyng drawing and its h scope is indicated by the appended claims.`

Referring to 'the drawing Figure 1 is a wiring diagram of a p micro-wave receiverincluding a Volume leveler of the biased crystal detector type,`

Figure 2 is a similar `diagram of a combined radio receiver and micro-wave transmitter, and Figure 3 illustrates theuse of an ammeter controlled Variometer for volume' leveling. v V The portable receiver of Fig. l includes an anterna s which is connected to a telephone head set ll 'through a tuned circuit 12 and a Crystal u detector !3. For the" purpose of automatically ortable leveling the Volume of the signal at the receiver I l, ,there is connected in shunt to this signalcchannel a crystal detector I4 and a bias potential source or battery !5. It will be noted that this receiving unit is Very small'and compact and that the only battery necessary for its operation is thedelay battery !5 which is subjectomy to charging current instead of discharging current. This battery is therefore very small and operates Satisfactorily for very long periods of time, the power consuming partsall being located at the microwave transmitter associated with the radio reu ceiver output or other transmitting unit. V

;I'I'he combined receiver and transmitter'of Fig. 2 includes a radio receiver IS which iscoupled through a transformer i? to a loudspealer [8. Also connected to the secondary winding of the output transformer l'l is a short wave transmitter comprising a short wave oscillator generator !9 which has its input and output circuits intercoupled through` a concentric line -21 and `is coupled through this line to an output antenna 22. Interposed between the transformer secondary are an impedance'device 23` and a switch for segregating the'transmitter when it is not in use.` The short wave receiver of Fig. 3 is similar to that of l' 'ig. 1 in several respectsbut differs therefrom in that the biased crystal detector is replaced by'a variometer 25 which is automatically operated by an ammeter mechanism 26 in response to the detected output of the receiver. The tuned circuit is resonant to the signal with the variometer in the position it assumes for Weak signals. Strong signals produce a greater rectified current through the ammeter movement, changing the position' of variometer 25, which in turn causes a detuning of the circuit through the g a change in inductance. This de-tuning keeps the radio frequency voltage applied to the crystal detector from becoming unduly large. It will be observed that this receiver does not involve the use of any batteries and will therefore be of very i light weight, and long life. i i

I claim as my invention: l A i '1. In a hearing aid system, the combination of a portable short waveradio receiver including an antenna, a variometer, a Crystal ,detector, a telephone receiver connected to said antenna through said detector and said variometer, and Volume leveling means connected inseries ,with and oper-` able in responseto the current of said telephone receiver to detunesaid variometer.

2. In a hearing aid system, the "combination i of a portable short wave radio receiver including ;55

receiver and means for automatically adjusting theimpedance of said variometer in response to the current of said telephone receiver.

3. In a' receiving system, the combination of a variometer and means for varying the impedance of said variometer, a motor, a detectortand a tele: phone receiver serially connected betweenpoints intermediate the ends` of 'saidvariometen said motor` being responsive to rectified Currents :from-` said detector and operatively ,onnected to said lmpedance varying means for automatically adjusting the impedance 'of said variometer.

4. In a high frequency recei'ving system, the combination including a variometer consisting of an inductor and a metallic disc movable in the plane of said inductor, a motor, a detector and a telephone receiver serially connected between points intermediate the ends' of said variometer, said motor being responsive to rectified currents irom said detector and operatively connected to 'said metallic disc for automatically moving said disctto control 'the 'amplitude of said rectified 'i current.

WINFIELD R. KOCH. 

